PURPOSE: To eliminate the need for regular or continuous monitoring of a metal vapor laser system by providing a monitoring device that indicates the state of a discharge tube, issues an alarm at a discharge failure, and generates signals for stopping the laser and for refilling gas.

CONSTITUTION: A discharge control device 10 includes a current probe 11 to detect current shunted from a charge current to a capacitor and from a discharge current of a discharge tube 8. The signal current detected by the probe is held at an instant a predetermined time after the beginning of a discharge. The held value is updated every discharge and indicated by a meter 13. The updated value of current is converted to an analog signal by a converter 12. If the analog signal exceeds a predetermined value, an alarm is given and d.c. power is cutoff. When the d.c. power is at low voltage, the converter 12 is disabled. This control device helps lighten operator's workload.